TNPSC Free Notes Chemistry – Acids, Base and Salts

இந்தக் கட்டுரையில், TNPSC குரூப் 1, குரூப் 2, குரூப் 2A, குரூப் 4 மாநிலப் போட்டித் தேர்வுகளான TNUSRB, TRB, TET, TNEB போன்றவற்றுக்கான  முறைகள் இலவசக் குறிப்புகளைப் பெறுவீர்கள்.தேர்வுக்கு தயாராவோர் இங்குள்ள பாடக்குறிப்புகளை படித்து பயன்பெற வாழ்த்துகிறோம்.

Acids, Base and Salts

Acids
 The substance which gives H + ions when dissolved it in water are called as Acids.
 They give Cations
 Their pH value is less than 7
 They convert blue litmus into red colour
 They have Sour taste
 Example: HCl, CH 3 COOH

Bases
 The substance which gives OH – ions when dissolved it in water are called as Bases.
 They give Anions
 Their pH value is greater than 7
 They convert Red litmus into blue colour
 They have Bitter taste
 NaOH, KOH
Theories
 Arrhenius Concept
 Bronsted Lowery concept
 Lewis Concept

Arrhenius Concept
 In 1884, a Swedish chemist Svante Arrhenius proposed a theory on acids and bases.
 According to Arrhenius theory, an acid is a substance which furnishes H+ ions or H 3 O+
ions in aqueous solution.
 They contain one or more replaceable hydrogen atoms.
 For example, when hydrogen chloride is dissolved in water, it gives H + and Cl – ions in
water.
 According to Arrhenius theory, bases are substances that ionise in water to form
hydroxyl ions (OH–).

 There are some metal oxides which give salt and water on reaction with acids. These are
also called bases.
 For example, Sodium hydroxide ionizes in water to give hydroxyl ions and thus get
dissolved in water.
Bronsted Lowery concept
 According to Bronsted lowery concept, the substance which gives or donates protons in
chemical reactions, such substance are called Acids.
 The substances which accept protons in a chemical reaction, such substance are called
as Base.
Lewis Concept
 According to lewis concept, the substance which accept a pair of electrons are called as
Acids.
 The substance which donate pair of electrons are called Base.
Indicators
Indicators are used to check whether a solution is acid or base by chemical reactions.

Acid, Base and Salts
PH – Scale
 pH scale is a scale for measuring the hydrogen ion concentration in a solution.
 The ‘p’ in pH stands for ‘Potenz’ in German meaning ‘power’.
 pH notation was devised by the Danish biochemist Sorensen in 1909.
 pH scale is a set of numbers from 0 to 14 which is used to indicate whether a solution is
acidic, basic or neutral.
 Acids have pH less than 7

 Bases have pH greater than 7
 A neutral solution has pH equal to 7
 pH = –log 10 [H + ]

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